Texas Petrochemicals LP

Transcription

1 Texas Petrochemicals LP The Leading Producer of C 4 Based Chemicals Butene-1 Distillation Control Project Tom Ellerbrock Optimization Engineer Texas Petrochemicals L.P. Texas Technology Showcase December 6, 2006

2 Summary Process description Old regulatory controls New regulatory controls Results & benefits Next steps 2

3 Butene-1 Project Objective Debottleneck B1 train to meet the increasing demand for highly profitable B1 production 3

4 C C C C Butene-2 Process Description ic 4 B=1, ic 4 H 2 C C C Butene-1 B=1 C Raff-2 BD, B=1 B=2, nc 4, ic 4 Hydrogenation B=1, B=2, nc 4, ic 4 B=1, trace nc 4 nc 4 C C C 1,3-Butadiene Raff-3 B=2, nc 4 C C C C C iso-butane C C C C n-butane 4

5 Old Regulatory Controls Hydrogenation Product B=1, B=2, nc 4, ic 4 B=1, ic 4 LC LC AI B=2, nc 4 5

6 Old Regulatory Controls Large swings in product flows and composition OH flow and composition (nc 4 ) affects downstream towers & performance Bottoms composition impacts Raff-3 total butylenes (C 4 =) Variable B=1 losses in bottoms stream Unknown effect of B=1 losses vs. column energy efficiency (BTU/lb) 6

7 Objective Revisited Debottleneck B1 train to meet the increasing demand for highly profitable B1 production Goals 1. Reduce B1 losses 2. Reduce OH variability 3. Improve energy efficiency 7

8 Variable Definition Evaluate controlled variables Relationship between B=1 purity and heat duty Non-linear 8

9 Heat Duty vs. B=1 Purity B-1 Recovery, % More energy req d for same change in recovery Energy Required, BTUs Significant incremental energy required to meet precise specifications 9

10 Variable Definition Evaluate controlled variables Relationship between B=1 purity and heat duty Non-linear Total C 4 = spec in Raff-3 product Bottoms blended with other stream to form Raff-3 Kept B=1 bottoms concentration between 1 15% Challenge existing targets Tower operated on basic level control Level cascaded to steam reboiler flow Manual composition adjustments Varying feed from Hydrogenation unit Varying Hydrogenation product composition (B=1, nc 4 ) 10

11 New Regulatory Controls (Primary) Analyzer modifications Added OH analyzer to measure nc 4 nc 4 composition controls OH flow Bottoms C 4 = analyzer used for control Calculate blended C 4 = in Raff-3 11

12 New Analyzers IRC Hydrogenation (nc Product 4 ) AI B=1, B=2, nc 4, ic 4 B=1, ic 4 LC LC AC B=1 recovery QC < AC Raff-3 C 4 = AI (ic 4 +B=1) B=2, nc 4 12

13 New Regulatory Controls (Primary) Analyzer modifications Added OH analyzer to measure nc 4 nc 4 composition controls OH flow Bottoms C 4 = analyzer used for control Calculate blended C 4 = in Raff-3 Control scheme changes Column heat duty controlled by either Raff-3 C 4 = or B=1 OH recovery Column level controlled by bottoms flow 13

14 New Composition Controls IRC Hydrogenation (nc Product 4 ) AI B=1, B=2, nc 4, ic 4 B=1, ic 4 LC LC AC B=1 recovery QC < AC Raff-3 C 4 = AI (ic 4 +B=1) B=2, nc 4 14

15 New Regulatory Controls (Primary) Analyzer modifications Added OH analyzer to measure nc 4 nc 4 composition controls OH flow Bottoms C 4 = analyzer used for control Control scheme changes Column heat duty controlled by either Raff-3 C 4 = or B=1 OH recovery Column level controlled by bottoms flow Minimized interaction between top and bottom compositions Reduced product flow and composition variability 15

16 New Regulatory Controls (Secondary) Internal reflux control Temperature-compensated flow Controlled by OH accumulator level 16

17 New Internal Reflux Control IRC Hydrogenation (nc Product 4 ) AI B=1, B=2, nc 4, ic 4 B=1, ic 4 LC LC AC B=1 recovery QC < AC Raff-3 C 4 = AI (ic 4 +B=1) B=2, nc 4 17

18 New Regulatory Controls (Secondary) Internal reflux control Temperature-compensated flow Controlled by OH accumulator level Hydrogenation feed forward signal Changes sent to heat duty controllers Hydrogenation feed flow Hydrogenation product B=1 % Hydrogenation product nc 4 % 18

19 New Feed Forward Control IRC Hydrogenation (nc Product 4 ) AI B=1, B=2, nc 4, ic 4 B=1, ic 4 LC LC AC B=1 recovery QC < AC Raff-3 C 4 = AI (ic 4 +B=1) B=2, nc 4 19

20 Project Results & Benefits 1. Reduce B1 losses 2. Reduce OH variability 3. Improve energy efficiency 20

21 B=1 Loss Reduction % of loss B1 Loss Avg Time 80% Reduction in B=1 Losses 57% Reduction in B=1 Variability 21

22 Project Results & Benefits 1. Reduce B1 losses $2.1 MM annual productivity improvement 2. Reduce OH variability 3. Improve energy efficiency 22

23 OH Composition Control nc4 OH Composition 1.5 % Time = 0.41 before controls = 0.04 after controls 23

24 Project Results & Benefits 1. Reduce B1 losses $2.1 MM annual productivity improvement 2. Reduce OH variability St.Dev. = Improve energy efficiency 24

25 Energy Efficiency Improvement Before after 85 Btu/lb % Production % 24% Reduction in Energy (Btu/lb) 65% Reduction in Energy Variability 25

26 Project Results & Benefits 1. Reduce B1 losses $2.1 MM annual productivity improvement 2. Reduce OH variability St.Dev. = Improve energy efficiency $950 M annual energy savings 26

27 Next Steps Develop energy vs. B=1 recovery model at varying energy prices Extend composition controls to downstream columns Develop B=1 train economic model Energy prices B=1 and Raff-3 prices Improve inventory control Minimize Hydrogenation feed flow changes 27

28 Texas Technology Showcase December 6, 2006 Tom Ellerbrock Optimization Engineer Texas Petrochemicals L.P. 28